\subsection{Sensitivity to the soil scheme}
\label{sec:sens-soil-scheme}

\subsubsection[ORCHIDEE 2-layers]{Running with ORCHIDEE 2-layers}
\label{sec:orchid_2}

Execute \verb+init.sh+ with \verb+veget=1+.  As explained in section
\ref{sec:setting-up-case}, the model is run automatically for one day
and creates a start file named \verb+sechiba_rest_in.nc+
(\verb+sechiba+ is the hydrological part of the soil/vegetation model
Orchidee).

Then you can run \verb+gcm.e+ to do a simulation with Orchidee
activated. The number of days, set in \verb+run.def+, is
\verb+nday=5+. To get results faster, decrease \verb+nday+ to 3, and
change \verb+5day+ in \verb+3day+ in \verb+config.def+, in the line
'\verb+phys_out_filetimesteps+' (otherwise your output file
\verb+histmth.nc+ will be empty).

You can play with the \verb+sechiba+ output frequency by changing in
\verb+orchidee.def+ the variable \verb+WRITE_STEP+ (in seconds;
default: \verb+86400+ for daily output); \verb+0+ means no
\verb+sechiba+ output; \verb+-1+ means monthly output; \verb+N*86400+
means output written every N days).  A second output file
\verb+sechiba_out_2.nc+ is for high-frequency output, modulated by
\verb+WRITE_STEP2+ (default: 10800, for 3 hours)

You can change the complexity level of outputs by playing with the
\verb+SECHIBA_HISTLEVEL+ variable: higher \verb+SECHIBA_HISTLEVEL+
means more variables in output.  The variables corresponding to the
various output levels are coded in
\begin{verbatim}
modipsl/modeles/ORCHIDEE/src_sechiba/intersurf.f90
\end{verbatim}

\subsubsection[ORCHIDEE 11-layers]{Running with ORCHIDEE 11-layers}

Set \verb+HYDROL_CWRR+ to \verb+y+ in \verb+orchidee.def+ (the default
is \verb+n+, meaning that ORCHIDEE 2-layers is used).

If it's the first time that you do a run with ORCHIDEE in your current
working directory (which is the case if you don't have a
\verb+sechiba_rest_in.nc+ file), the procedure is the same as
described in § \ref{sec:orchid_2} for ORCHIDEE 2-layers.

If you have already done a run with ORCHIDEE -2 layers, you need to re-create
an initial state file adapted to the multi-layer hydrology: 
\begin{enumerate}
\item remove the file \verb+sechiba_rest_in.nc+ in your working
  directory,
\item set \verb+SECHIBA_restart_in.nc+ to \verb+NONE+ in orchidee.def,
  and
\item relaunch the gcm.
\end{enumerate}

\subsubsection[Bucket]{Running with the simple bucket scheme}
\label{sec:bucket}

If \verb+VEGET=n+ (meaning that the vegetation is not activated) instead
of \verb+y+ in file \verb+config.def+, the soil scheme is a simple
bucket (even if you compiled with \verb+makegcm -v true+ as done by
\verb+install.sh+ when ran with \verb+veget=1+).

\subsubsection[Bucket scheme with imposed soil water
  content]{Running with bucket scheme with imposed soil water
  content}

Same as in § \ref{sec:bucket}, you should run with \verb+VEGET=n+ in
\verb+config.def+.  Evaporation is computed as the potential
evaporation multiplied by the aridity coefficient \verb+vbeta+, which
is a function of the soil water content \verb+qsol0+:
\begin{verbatim}
vbeta(i) = MIN(2.0*qsol/mx_eau_sol, 1.0)
\end{verbatim}
(here \verb+mx_eau_sol=150mm+ ). So, if \verb+qsol0+ is constant,
\verb+vbeta+ is constant as well.  You can fix \verb+qsol0+ to a
chosen value \verb+qsol0_val+ (in mm), by adding in \verb+physiq.def+
the line \verb+qsol0=qsol0_val+ ; try for example \verb+qsol0_val=5+
or \verb+10+, that result in \verb+vbeta+ values typical of
summertime.

You can compare the turbulent fluxes for the austral summer (variables
\verb+flat+ and \verb+sens+ in the LMZ output files) computed using
the different options.

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